Well, as you may have noticed from the lack of articles I have had a bit of a break from Britonia in the last three months. I’ve had a few things to sort out in real life, I’ve just brought a house and should be moving in in a few months, and I’ve been sorting out a few things for work. There are a few little updates though ..

I have wanted to expand on my previous post regarding ‘Cube to Sphere Projection’ for a while now, so in this article I am going to cover how I define the spherical geometry of the planets in more detail.

I decided to write this article in response to a comment by Robert on my previous ‘Ship Lists’ article. He brought up the fact that just calculating the specific physical properties of a ship doesn’t tell the whole story of space flight without first considering fuel and payload. You can read the original comment here.

Quite honestly I glossed over the fuel and payload section in the previous article because I knew it would be a problem and I hadn’t quite decided yet how to handle the issues in-game. The question is of course “how realistic will the game be in terms of fuel and fuel consumption”? and “will be by fun/entertaining for the player to fill up the cargo hold full of fuel just to be able to leave the atmosphere of a planet”?

The three approaches which are most obvious at this stage are:

1) Simulate Realistic Physics and Fuel Consumption : This is certainly an appealing approach and a lot of people would perhaps admire such a simulation for its realism, but will definately be off-putting for casual gamers. Furthermore, accurately simulating spacecraft using real physics models is extremely complex and involve many factors; all of which aren’t really feasible or a benefit to simulate. This would also introduce issues of ship design. As an example, the thrusters required for huge spacecraft to launch would themselves be huge; and would have to appear to scale on the ship. Add to this the need to place thrusters all around the ship for rotating and ‘strafing’ etc. and the ships will no longer look slick and cool (yes cool) but like big masses of ugly efficient-functionality.

A few other less-than-fun issues introduced with this system are ‘what do you do if the player runs out of fuel?’ As always there are a few ways of handling this, but short of actually waiting for someone to come and pick you up would break the realism we were striving to achive in the first place. This is a concern.

2) Forgo Fuel Consumption: This approach was adopted in the Elite series whereby conventional thrusters didn’t require fuel for acceleration; and this definiately had its merits. For one, the player only needed to concern his/herself with purchasing fuel for hyperjumps to use the jump drive and there was nothing overly complicated with taking off and leaving a planet. Just ‘launch’, rotate the ship upwards and fire! As you can read in Robert’s previous comments, this eliminates the issue of taking off within a the gravational area of a planet.

3) Use a mixture of the two above. : Now I’m all for realism and I’ve read a lot of comments which go both ways on just how real to simulate things like this, but I’m just not convinced that simulating real space flight dynamics will be fun for the player. Also, to pass up the issue of fuel will remove some of the element of ‘danger’ and planning I think has the potential to be enjoyable. So at the minute I plan on using a mixture of the above, but perhaps a little differently than tradional space sim games.

I am thinking about including three different engines types for flight, each of which will be mountable in one ship thruster slow/position. Here are the three types (not including Jump-Drives):

ION/Plasma Trusters

ION thrusters are used in real life for long distance space flight. They are typically favoured because of the relatively low fuel consumption when compared to traditional chemical engines. This improvement in fuel consumption is because electic thrusters typically offer much higher specific impulse (this represents the change in momentum per unit amount of fuel).

There are a few draw backs with ION thrusters though, which when implemented in the game will lucky add a little diversity. The first draw back is that they don’t provide as much thrust compared to chemical thrusters due to practical power source contraints. The second draw back is that they only work in environments that are void of ionized particles, so if you decide to equip just ION thrusters on your ship, you wont be able to land on planets with atmospheres.

There are three kinds of ION thruster in real life (Electromagnetic, Electrothermal/Plasma and Electrostatic). There will be diferent ION trusters available within the game but the differences will be purely cosmetic (different thruster description, different coloured beam), with all thrusters performing with the same characteristics:

Pros :
Low fuel consumption (read: no-fuel consumption)

Cons :
Cannot fly within atmosheres
Low thrust (force) output

Summary :
A good option for beginning players as the there is no need to worry about fuel consumption and/or running out. Hopefully more experienced players will want to eventually opt for more power chemical thrusters for greater acceration.

Chemical Rocket Thrusters

Currently all spacecraft use chemical rockets for launch. Chemical thrusters require a large amount of fuel to operate, but provide consideratly more thrust than ION thrusters. In the context of the game, chemical thrusters will be required to navigate within the atmosphere of a planet, and will indeed require fuel to do so, although the fuel consumption may not be realistic:

Pros :
Provides much more power compared to the ION thruster.
Functions in atmospheric conditions (i.e. planets with atmospheres).

Cons :
Requires fuel.
Would be plausible that the player can run-out of fuel and thus would need rescuing.

Summary :
A good choice for players who want faster ships but requires a little more journey planning and management of fuel.

Hybrid Thrusters
Whilst perhaps not currently technically possible I would like to include some kind of hybrid technology to make the game more sympathetic to new players who perhaps don’t want the hassile of outfitting different ships and just want to ‘shoot things’. The hybrid engines will non consume fuel in outerspace, and will require significantly less fuel when within a gravatational area. This will come at the expense of having significantly lower thrust outputs then the chemical or ION/plasma thrusters.

Pros :
Offers both the benefit of power provided by the chemical engine and the ease of mind of a fuel-less alternative for emergencies.
No restricts on environment conditions

Cons :
Provides less acceleration than either the electric or chemical engines of the same class.

To Sum Up

So hopefully with the details mentioned above it should be a little clearer to see what I intend to do. If you decide you want to outfit one ship for space dog-fighting, then you may want to use chemical rocket engines and refuel often for the advantage of higher accelertion. If you are a trader, then perhaps ION thrusters would be beneficial considering you needn’t worry about fuel on long journeys. The last question which I haven’t address yet is the actual consumption of the chemical engines, however this will be fun-factor based so its a little too early to say.

In this article I’ll be speaking about what I’ve been up to with regards to researching and defining the dimensions and specifications of the ships and engines. I aim to have engines and ship sizes which are both believable in size and capabilities, while not necessarily being so accurate as to be confusing for the player. I’m writing this simultaneously with the ships list.

For the last three weeks I have started modeling the first in-game content for Horizons, the ‘Locust MK I’, using Blender3D and paint.NET. This time round, I’ll go over how I am exporting model and opaque data from blender, texturing the model with UV maps and paint.NET and importing them into XNA.

A lot of developers I speak to often ask if I use a form of SVN (SVN wikipedia) and when I answer in the negative, they usually tell me of the benefits of doing so. Now I haven’t used it (much) before and I’ve never really had a reason to, being that I am working alone on Britonia and I only really use my main computer for development. But I thought, if everyone’s doing it, maybe there are unseen benefits …

So I had a look around on the weekend for project hosting sites which offered free hosting using SVN, and I found a few. Many of the project hosting sites however only offer only free hosting to open source projects, but I did manage to find one called ProjectLocker. It seems to have everything I could need for hosting my project privately and it also offers an intergrating Trac system. So I thought I’d give it a go.

For anybody who hasn’t heard of SVN, basically it offers a way to host your entire project (minus build and object files) on a server and using a tool like TortoiseSVN in windows, you can quick and easily download (checkout) or backup (commit) changes to this one central repository. It also keeps a copy of all versions of a file and logs changes made.

This makes it easy if say, you want to work on your project from several locations, or you have multiple developers working on a project.

For now, while I still haven’t setup it all up – I am hoping that the Trac system will help me focus on specific enhancements and bugs in Britonia. I’m finding that when I sit down I spend a good 1-2 hours just playing with what is already ‘working’; tweaking the heightmaps, changing scattering colours, flying around the planets etc.

If you want to try it out, here are a few links to the tools which I am using :